A method is disclosed for modifying a catalytic molecular sieve for shape-.sdcciivc hytlrocarbon conversions comprises: selectivating said catalytic molecular sieve by contacting wiih silicon containing selectivating accnt; and b) calcining the selectivated catalytic molecular sieve at high temperature calcination conditions comprising temperatures greater than 700C which conditions are sufficient to reduce acid activity as measured by alpha value and increase diffusion barrier of said catalytic molecular sieve as measured hy the rate of 2,3-dimethylbulane up take, as compared, to the sclectivaled catalyst. Calylic molecular sieves thus prepared, such as si licit-bound 2SM-5, and their use in hydrocarbon conversion processes such us aromatics isomerization, e.g., xylene isomerzation, ethylbenzene conversion and aromntics disproporlinnatior.g., toluene disproipononation are also disclosed.
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